feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

internal/pkg/dto/request/support_availability_req.go

@@ -0,0 +1,34 @@
+package request
+
+import "agent-desk/internal/pkg/enums"
+
+type SupportCalendarPeriod struct {
+	Start string `json:"start"`
+	End   string `json:"end"`
+}
+type SupportCalendarWeeklyPeriod struct {
+	Weekday int `json:"weekday"`
+	SupportCalendarPeriod
+}
+type SupportCalendarException struct {
+	Date    string                  `json:"date"`
+	Closed  bool                    `json:"closed"`
+	Periods []SupportCalendarPeriod `json:"periods"`
+}
+type SupportCalendarRequest struct {
+	TeamID     int64                         `json:"teamId"`
+	Mode       string                        `json:"mode"`
+	Timezone   string                        `json:"timezone"`
+	Weekly     []SupportCalendarWeeklyPeriod `json:"weekly"`
+	Exceptions []SupportCalendarException    `json:"exceptions"`
+}
+type SupportCalendarPreviewRequest struct {
+	Calendar SupportCalendarRequest `json:"calendar"`
+	At       string                 `json:"at"`
+}
+type SupportAvailabilityRequest struct {
+	UserID         int64               `json:"userId"`
+	ServiceStatus  enums.ServiceStatus `json:"serviceStatus"`
+	AbsenceStartAt string              `json:"absenceStartAt"`
+	AbsenceEndAt   string              `json:"absenceEndAt"`
+}